A known door latch apparatus for a vehicle such as disclosed in JP10-266667A includes a close power transmitting mechanism for transmitting a rotational power of an electric motor in one direction to a latch so as to drive the latch to rotate in a lock direction where the latch further engages with a striker, thereby shifting a door from a half-latched state to a fully closed state. The aforementioned door latch apparatus generally includes an active rotary member connected to an output shaft of the motor and rotatable in a reciprocating manner within a rotation range specified beforehand. The active rotary member is driven to rotate in one direction by the rotational power of the motor in one direction when the door is in the half-latched state, for example. The active rotary member rotates from a close member contact position where the active rotary member is in contact with a portion of the close power transmitting mechanism to a close completion position by moving from the close power transmitting mechanism by a predetermined close operation angle. As a result, the rotational power of the motor is transmitted to the latch via the close power transmitting mechanism to thereby drive the latch to rotate in the lock direction (i.e., a close operation).
According to the aforementioned door latch apparatus, after the close operation, the active rotary member is required to be positioned away from the close power transmitting mechanism in a normal state, i.e., when the close operation is not performed, so as not to hinder a door opening operation by keeping contact with the close power transmitting mechanism. Thus, the rotation range of the active rotary member includes a standby area of which both ends are defined by the close member contact position and a close member maximum separation position that is away from the close member contact position in the other direction by a predetermined inoperative angle.
FIG. 23A conceptually illustrates the standby area and the rotation range of the active rotary member. As illustrated in FIG. 23A, a standby area Q is defined at one side within a rotation range P. According to the aforementioned explanation, the standby area Q is necessary, however, the large standby area Q may induce an enlargement of the door latch apparatus. Thus, it is desirable for the standby area Q to be minimized. Further, in order to securely position the active rotary member within the standby area in the normal state, a detecting means is inevitable to detect whether or not the active rotary member is positioned within the standby area Q. In order to minimize the standby area, the detecting means having an excellent accuracy and thus being expensive is required. However, because of a high cost competition of these days, the door latch apparatus manufactured at a low cost by reducing a cost relating to the detecting means is desired.
On the other hand, a different structure is considerable in which a driven rotation member is provided for rotating in conjunction with the active rotary member over the entire rotation range of the active rotary member. The driven rotation member rotates wider than the active rotary member. Whether or not the active rotary member is positioned within the standby area is detected by a detection of a position of the driven rotation member.
In connection with the above, JP10-266667A discloses a latch and a rotary lever rotatably provided at a side of the latch. The latch and the rotary lever are connected by means of a cam projection and a cam groove so as to be rotatable in conjunction with each other. A rotation position of the latch is detected as a rotation position of the rotary lever. Then, when the latch is positioned at a center of the rotation range, the cam projection is positioned on a reference line connecting a rotation center of the latch and a rotation center of the rotary lever. At this time, the cam groove also overlaps the same reference line so that the cam groove is in parallel with the reference line. As a result, an overall length of the rotary lever is configured to be shortened. However, because the latch rotates rapidly at a time of opening or closing of the door, the rotary lever and the detecting means are required to have durability against the rapid rotation of the latch, which may prevent a reduction of cost.
Further, in a case where the latch is simply replaced by the active rotary member for applying a technology disclosed in JP10-266667A to a position detection of the active rotary member, the following structure is obtained. As illustrated in FIG. 23B, a cam projection 3 is positioned on a reference line S1 connecting a rotation center 1A of an active rotary member 1 and a rotation center 2A of a rotary lever 2 when the active rotary member 1 is positioned at a center of the rotation range P. At this time, a cam groove 4 provided at the rotary lever 2 is in parallel with the reference line S1 in a state where the cam groove 4 overlaps the reference line S1. In such structure, a rotation angle of the rotary lever 2 per unit rotation angle of the active rotary member 1 is largest in the vicinity of the center of the rotation range P. The rotation angle of the rotary lever 2 is gradually decreasing towards the vicinity of both ends of the rotation range P from the center thereof. Thus, within the standby area Q defined at one side within the rotation range P, the rotation angle of the rotary lever 2 while the active rotary member 1 rotates from one end to the other end of the standby area Q is small. As a result, even for detecting whether or not the rotary lever 2 is positioned within the standby area Q, the detecting means having the high accuracy is required.
A need thus exists for a door latch apparatus for a vehicle which is not susceptible to the drawback mentioned above.